The present disclosure relates to the recovery of hydrocarbons in certain oil and gas field developments wherein the hydrocarbons are contained within one or a multitude of low permeability, tight reservoirs which require advanced drilling and completion techniques such as multi-lateral well construction with fracture stimulated completions in order to establish commercial production. In these environments, the hydrocarbons are often dispersed in a stacked sequence of tight, hydrocarbon-bearing reservoirs (i.e., sandstones, carbonates, or brittle shales having high organic carbon content) together with impermeable, non-productive formations (i.e., ductile shales or salts). Due to the relatively small size of each reservoir compartment and/or limited drainage ability of completions targeting these hydrocarbon-bearing reservoirs, comingling of many separate zones into a single completion with the downhole pump of an artificial lift system placed below the completed reservoirs is often required to achieve efficient and economic exploitation.
In some cases, these tight reservoirs have substantially vertical-oriented natural fractures which enhance the production potential of the well completions when the natural fractures are effectively communicated with the well by a wellbore penetration and/or hydraulic fracture stimulation treatment. Penetrating a vertically-oriented natural fracture with a substantially vertical wellbore is difficult. Additionally, it is difficult to effectively propagate an induced hydraulic fracture away from a substantially vertical wellbore in a direction which will allow for interception with vertically-oriented natural fractures when the azimuth direction of the natural fractures is substantially parallel with the present-day maximum principal horizontal stress direction. In these cases, the induced hydraulic fracture will typically be oriented parallel with the natural fractures and thus will not intercept or otherwise communicate the substantially vertical wellbore with the natural fractures. An obvious solution to this problem is to drill a horizontal wellbore in a direction which will allow for interception with the natural fractures, but using conventional short, medium, or long radius horizontal drilling technology to accomplish this goal is not practical because of the number of such horizontal wellbores which would be required to exploit the multiple stacked reservoir compartments.
In other cases, the tight reservoirs are not substantially naturally fractured and contain hydrocarbons primarily in micro-pores contained in the tight reservoir rock matrix. In many of these situations, commercial production can only be established through effective fracture stimulation of horizontal lateral wellbores. These fracture stimulated lateral completions are designed to maximize exposure of the tight reservoir with the wells and the stimulated reservoir volume connected to the well completion. However, in many cases the hydrocarbons located within a single reservoir compartment are not present in sufficient quantities to justify drilling and completing a conventional short, medium, or long radius horizontal wellbore with fracture stimulation treatment targeting a single reservoir compartment due to the cost associated with such conventional exploitation methodology. Additionally, in some cases the strata located in close proximity above or below the targeted reservoir compartment contain excessive quantities of formation water. In many of these cases, there are not sufficient barriers to contain fracture height growth within the targeted reservoir compartment if conventional massive hydraulic fracture stimulation techniques are utilized.
To address these challenges, new drilling and completion approaches are required that allow for low cost construction of multi-lateral wells with fracture stimulation treatments that allow for effectively communicating the wells with natural fracture systems contained within multiple stacked reservoirs. New multi-lateral well construction approaches are also needed for maximizing stimulated reservoir volume while avoiding the creation of induced hydraulic fractures which extend into the adjacent water-bearing formations or which otherwise fracture out-of-zone.
The present disclosure relates generally to equipment utilized and operations performed in conjunction with the construction of subterranean wells having a multitude of ultra-short radius lateral wellbores extending from cased main or parent wellbores to intercept natural fractures and/or to maximize exposure of the wells with a multitude of subterranean formations containing hydrocarbons or other valuable materials. In an embodiment described herein, the disclosure more particularly provides systems and methods for stimulating and producing parent wells having multiple lateral wellbores in order to complete multiple reservoir compartments for a comingled production with a downhole pump located below all completed reservoirs and to maximize the stimulated reservoir volume of each completed reservoir. The methods of this disclosure will provide for interception of vertically oriented natural fractures and/or effectively creating complex induced fractures in the targeted reservoirs while avoiding growing fractures into adjacent water-bearing formations or other non-productive strata. The system and methods of the present disclosure also provide for selective isolation of specific completed zones or reservoirs which are found to produce excessive quantities of formation water after completion with a lateral wellbore and/or a fracture stimulation treatment.
Improvements are continually needed in the arts of drilling and stimulating multi-lateral wells. For example, one technique for drilling lateral wellbores involves the use of a drilling assembly which is capable of drilling “ultra-short” radius lateral wellbores. The present specification is not limited to this particular ultra-short radius wellbore drilling art, but it is useful to demonstrate examples of the kinds of improvements needed.
In the ultra-short radius wellbore construction art, a lateral wellbore is typically drilled or jetted from a parent wellbore with a turn radius from vertical to horizontal (i.e., 90 degrees) in less than 5 feet. The parent wellbore is in many cases lined with a casing string made of a very strong and durable material, such as steel. Usually external to the casing string is a cement material which is hard and brittle, with relatively high compressive strength to provide for isolation between hydrocarbon-bearing zones as well as other formations in the annulus between the casing string and the wellbore.
It is generally necessary to mill, drill or otherwise cut through the casing string and the cement with one type of assembly, retrieve the assembly, and then use another type of assembly for drilling the lateral wellbore. This procedure is time-consuming (and, therefore, expensive) and requires that multiple assemblies be accurately aligned with respect to the casing string and targeted hydrocarbon-bearing zones in order for the successful construction of the lateral wellbore. These problems are compounded when multiple lateral wellbores are to be drilled from the same parent wellbore into one or a multitude of hydrocarbon-bearing zones. Additionally, when ultra-short radius drilling techniques are employed, limitations exist in the current art for cutting through casing strings comprised of relatively hard steel (i.e., greater than grade N-80 pipe) or thick walled pipe (i.e., greater than 1 cm).
Furthermore, adequate systems and methods have not been developed for stimulating the one or more zones completed from a parent well with a multitude of ultra-short radius laterals. For example, one of the problems encountered in the ultra-short radius wellbore construction art is that the lateral wellbores drilled or jetted using the technique are generally relatively small in diameter, and so typical stimulation equipment and procedures cannot be used effectively. In addition, the relatively large number of lateral wellbores to be stimulated means that it is very time-consuming (and, therefore, expensive) to individually stimulate the zones or reservoirs intersected by each wellbore.
The disadvantages of the prior art are overcome by the present disclosure, and an improved system and method are hereinafter disclosed for constructing and fracture stimulating multi-laterals from a parent well.